The present invention, which is referred to as the DEV Cycle Engine, is designed to substantially improve the performance of internal combustion engines by improving combustion and extraction of energy from these engines. The focus of this invention relates to recovering more energy from combustion of an air-hydrocarbon fuel-mixture (hereafter called Air/Fuel mixture) or another types of fuel mixtures such as an hydrogen/oxygen or other fuel mixtures that are supplied to an internal combustion engine. It has been known that a large expansion ratio, that is the ratio of the volume of the combusted gases after expansion in the engine to the volume of the combusted gases at their maximum pressure in the combustion chamber, will extract more energy from the above Air/Fuel mixture and that the thermodynamic efficiency increases as the expansion ratio increases.
Most present day internal combustion engines have the same compression and expansion ratios due to inherent mechanical and combustion considerations. The compression ratio of a typical Otto cycle engine using gasoline as a fuel is usually limited to a range of values from 8 to 1 with an upper limit of approximately 12 to 1 depending upon such factors as the fuel mixture, fuel initial temperature just prior to compression, fuel “octane rating”, power requirements needed, mechanical shape of the compression chamber, “hot spots”, poor cooling of surfaces, and other considerations. For diesel fueled engines the typical compression ratio is approximately 16 to 1 and upwards to around 22 to 1 with much the same restrictions as for the gasoline engine. Other fuels present similar limitations.
Thermodynamics shows that compressing any gas (or any gas mixture) causes both the pressure and temperature of the gas to rise due to the energy added to the gas (from work performed compressing the gas). All combustible mixtures have a “kindling temperature” and upon reaching that temperature it will self-ignite. That self-ignition phenomenon, in an Otto Cycle engine, is known as “knocking” or “pinging” and can cause damage to the engine if allowed to continuously occur. In a diesel engine, that specific characteristic is used to spontaneously ignite the fuel. The typical sound of the diesel engine is the explosion of the fuel instead of igniting via a spark plug and then slowly (a few milliseconds) burning as in the Otto cycle.
Several techniques have been described in various patents that provide a method to “stretch” the compression restriction by providing a spring loaded piston connected to the main compression chamber such that as the compression pressure reaches a predetermined level it will cause the spring loaded piston to move in such a manner that effectively increases the “clearance volume” of the compression chamber and thereby limiting the pressure (somewhat) so that “knocking” does not occur. To a degree, the expansion ratio has been slightly increased thereby achieving an increase in efficiency.
(See U.S. Pat. Nos. 5,341,771 and 5,970,944).
In other attempts to gain better fuel economy a “pre-combustion chamber” is utilized to allow better ignition of a small quantity of Air/Fuel mixture which then is used to ignite the balance of the fuel in the main power combustion chamber. In some cases the pre-combustion chamber is used to provide a “richer Air/Fuel mixture thereby allowing a “poorer” gas mixture, in the main power combustion chamber piston area, to be “reliably” ignited. (See U.S. Pat. No. 4,864,989). Sometimes the pre-combustion chamber is used to avoid significant mixing of a portion of the new fresh Air/Fuel mixture with spent “old burned gases” that would “dilute” the next new mixture decreasing the overall efficiency of the combustion process and reducing the utilization of the energy stored in the fuel (See U.S. Pat. No. 3,967,611). These “old burned gasses” occur because of incomplete purging of the power cylinder chamber at the end of the exhaust stroke.
Other prior patents have utilized complex mechanical methods to vary the clearance volume at the top of the stroke by raising or lowering the pistons, crankshaft and portions of the drive train (i.e. transmission) when low power demands of the engine allow a smaller amount of fuel to enter combustion volume. This also requires that the operation of the intake and exhaust valves be simultaneously modified to maintain the compression ratio such that it stays below the spontaneous ignition point. (See U.S. Pat. No. 4,174,683).
Other patents vary the intake valve timing that allows “over-lapping” of the intake valve with the compression stroke, thereby effectively changing the “apparent” compression ratio. Accompanying the varying intake valve closing procedure is an auxiliary spring loaded (or hydraulic positioning) piston to vary the “clearance volume” above the “power piston” head such that the compression stroke is maintained at a low enough value that is below the spontaneous ignition point. (See U.S. Pat. Nos. 4,033,304 and 4,138,973).
In U.S. Pat. No. 6,073,605, the main combustion chamber only contains air, as the compression stroke nears the “top-dead-center” position (hereafter referred to as TDC), the temperature of the air has been raised to a very high temperature and pressure. Next, when the inter connecting valve (between the pre-combustion chamber and the main combustion chamber that includes the power piston chamber) is opened, the high pressure (and high temperature) air rushes into the pre-combustion chamber and ignites the fuel. This type of arrangement has several problems including incomplete burning of fuel due to incomplete mixing of air and fuel and also the extreme velocities of very hot gasses that would erode the valve mechanism between the chambers.